Surge diverters



June 11, 1963 A. D. MILLER SURGE DIVERTERS Filed May 2, 1958 United States Patent 3,093,772 Fatented June 11, 1963 3,093,772 SURGE DEVERTERS Alan David Miller, Wigan, England, assignor to Associated Electrical Industries (Manchester) Limited, a

British company Filed May 2, 1958, Ser. No. 732,529 Claims priority, application Great Britain May 9, 1957 2 Claims. (til. 317-75) This invention relates to surge diverter devices and aims at providing an improved arrangement suitable to overcome difiiculties which have been experienced up to now with conventional protecting devices where electric apparatus and machinery, particularly of the A.C. kind, have to be safeguarded against the destructive effect of voltage and current surges. The new device ensures rapid current interruption at commercial frequency which safely prevents follow current, and permits to derive the full advantage of a close tolerance setting of the spark gaps. Thus greater safety and reliability of operation at a predetermined voltage can be ensured, which in turn makes it possible to achieve savings in space, material and costs, as the dielectric strength of the insulation used in the circuit to be protected, such as machinery, apparatus distribution lines and so on can be more closely defined.

This is achieved by a vacuum switch arranged in series circuit relationship with at least one spark gap, and a nonlinear resistance, the switch opening means including a coil which is connected in parallel to a portion at least of said resistance. As the ohmic effect of the resistance decreases with current increase, the operating coil is safeguarded against damage by surges, and this enhances the reliability of operation.

More especially the invention provides a means for safe and reliable interruption of the follow current by using in conjunction with a spark gap means a circuit breaker of the rapid action vacuum type and has its operating coil energised with a voltage which cannot rise to a value dangerous to the coil insulation even if the current flowing through the spark gap rises to an excessive value. Thus the operation of the surge diverter is made more effective and more reliable than could be achieved with constructions known and used up to now, while the new device is also economical and space saving.

Accordingly, the present invention resides in the provision of a surge diverter comprising in series circuit relationship at least one sparking gap, a resistance, and contacts of a circuit breaker wherein the circuit breaker is of the vacuum type and wherein the energizing coil of the circuit breaker is connected in parallel to a resistance which has a non-linear, decreasing ohmic value with current increase so as to limit the voltage applied to the operating coil of the circuit breaker.

In a preferred embodiment the energising coil of the circuit breaker is connected in parallel to a portion only of the non-linear resistance.

The invention will be better understood from the accompanying drawing, in which:

FIG. 1 shows by way of example a preferred embodiment of a surge diverter according to the invention; and

FIG. 2 shows graphs explaining its operation.

Referring to FIG. 1 the circuit to be protected, such as a high voltage transmission line 1, is connected to earth through a spark gap arrangement 2 and a non-linear resistance, conventionally formed by a stack of series connected discs of non-linear resistance material the ohmic value of which decreases as the current flowing through it increases as known in the art. In the present case this resistance is shown as comprising two sections 3, 4. According to the invention a vacuum circuit breaker 5 of known construction is connected in series circuit relationship, preferably between the two resistance sections, 3, 4 and its energising coil 6 is connected in parallel to the resistance section 4.

In FIG. 2 the A.C. voltage wave on the transmission line is denoted a, and the current wave flowing through the surge diverter is denoted b. When surge occurs the value of this current rises to a peak 0. After the surge the shape of the current Wave b becomes similar to that of a as shown by the graph. Now the follow current is definitely and safely interrupted by the breaker 5 at the first or second zero point e, or f of the wave b.

it will be understood that details of the arrangement shown can be varied without departing from this invention as defined by the appended claims. For instance the non-linear resistance need not be sub-divided, and if it is subdivided the ener-gising coil of the vacuum circuit breaker could be connected across the section 3 instead of across section 4 shown in FIG. 1.

What I claim is:

1. A surge diverter comprising for connection between an A.C. circuit and earth, a series arrangement of at least two switch contacts, at least one spark gap, and a nonlinear resistance whose ohmic value decreases as the current traversing it increases, means providing a vacuum space in which said contacts are mounted, and means for effecting switch opening comprising an operating coil, said coil being connected parallel to a portion at least of said resistance.

2. A device as claimed in claim 1, wherein the contacts of the vacuum switch are connected between two portions of the non-linear resistance.

References Cited in the file of this patent UNITED STATES PATENTS 811,226 Jones Jan. 30, 1906 2,288,050 Vatter June 30, 1942 2,892,912 Greenwood June 30, 1959 2,920,169 Jennings Jan. 5, 1960 FOREIGN PATENTS 161,675 Switzerland July 17, 1933 

1. A SURGE DIVERTER COMPRISING FOR CONNECTION BETWEEN AN A.C. CIRCUIT AND EARTH, A SERIES ARRANGEMENT OF AT LEAST TWO SWITCH CONTACTS, AT LEAST ONE SPARK GAP, AND A NONLINEAR RESISTANCE WHOSE OHMIC VALUE DECREASES AS THE CURRENT TRAVERSING IT INCREASES, MEANS PROVIDING A VACUUM SPACE IN WHICH SAID CONTACTS ARE MOUNTED, AND MEANS FOR EFFECTING SWITCH OPENING COMPRISING AN OPERATING COIL, SAID COIL BEING CONNECTED PARALLEL TO A PORTION AT LEAST OF SAID RESISTANCE. 